The present invention relates generally to methods and apparatuses for coding images and intra coding of video and more particularly to a method and apparatus for coding images and intra coding of video using transform coding. Intra coding is important for applications requiring simple encoding/decoding, low delay, a high degree of error robustness or a high level of interactivity. Examples of such applications include image/video on the Internet, wireless video, networked video games, etc.
The state of the art standards in image coding and intra coding of video employ transform coding (e.g., Discrete Cosine Transformation, DCT), which involves partitioning an image into non-overlapping blocks of 8.times.8 size and coding in units of a 2.times.2 array of luminance (Y) blocks and a corresponding chrominance block of Cr and a block of Cb signal (together referred to as a macroblock). Improvements in performance of intra coding have been obtained by predicting the DC coefficient of DCT blocks by using previously reconstructed DC coefficients. Recently, further improvements have been obtained in MPEG-4 by predicting AC coefficients as well.
Over the past several years, many researchers have followed a different approach that uses wavelets instead of transform coding. These researchers have reported substantial improvements, at the expense of increased complexity. Recently, variations of wavelet coding that use subsampling prior to coding have emerged (some of which are currently being experimented with in MPEG-4), that provide an even higher performance by using advanced quantization techniques that take advantage of subsampling, however, the complexity of such schemes is extremely high.
The present invention is therefore directed to the problem of developing a method and apparatus for coding images and video that has a high coding efficiency yet relatively low coding complexity.